Fabrication of a Sandwiched Core Carbon Sphere@Na₃V₂(PO₄)₂O₂F@N-Doped Carbon Cathode for Superior Sodium-Ion Batteries

Abstract

Cathode materials play a decisive role in the building of high energy density sodium-ion batteries. Among them, Na3V2(PO4)2O2F (NVPOF) is receiving active attention due to its high structural integrity, satisfactory work voltage, and outstanding energy density. However, its practical application is still impeded by the poor rate performance related to its low intrinsic electronic conductivity. Herein, Na3V2(PO4)2O2F grown on the surface of the core carbon sphere (CS@NVPOF) was initially synthesized via a one-step hydrothermal method. Subsequently, by carbonization of polydopamine, the above particles coated with a uniform N-doped carbon layer (CS@NVPOF@NC) were successfully fabricated. This sandwiched structure built by a core carbon sphere and carbon layer can significantly improve the electronic conductivity, boost sodium-ion diffusion kinetics, and mitigate volume change of the electrode upon the cycling process. As a result, the as-prepared electrode exhibits a desirable specific capacity of 119.8 mA h g–1 with an attractive capacity retention of 96% after 100 cycles at a current density of 1 C. Even at a high current density of 10 C, the capacity can retain 103.9 mA h g–1, and the capacity decay per cycle is only 0.032% during 500 cycles, indicating outstanding electrochemical performance. All the analyses demonstrate that CS@NVPOF@NC has enormous potential as an applicable cathode for sodium-ion batteries.

“Three‐in‐One” Strategy that Ensures V2O5·nH2O with Superior Zn2+ Storage by Simultaneous Protonated Polyaniline Intercalation and Encapsulation

“…The CV method (Figure 3b) in the voltage range of 0.2–1.6 V (vs. Zn 2+ /Zn) of Zn//P‐VOH@P cell depicts the shape transformation with the increase in scan rates. At 0.2 mV s −1 , in addition to the two pairs of typical peaks (0.57/0.42 and 0.98/0.88 V) on account of the two‐step Zn 2+ insertion/extraction with the redox reactions of V 4+ /V 3+ and V 5+ /V 4+ , another redox peak pair is seen at about 0.80/0.72 V. [ 52 ] It is probably because PANI also participates in the energy‐storage process, while the increasing overpotential at large scan rates makes the redox peaks of polyaniline offset and overlap with the redox peaks of VOH. [ 53 ] Meanwhile, the peak current ( i , mA) and the scan rate ( v , mV s −1 ) conform to the following formula, (1) and (2), with a and b as parameters.…”

High-Rate-Capacity Cathode Based on Zn-Doped and Carbonized Polyacrylonitrile-Coated Na4MnV(PO4)3 for Sodium-Ion Batteries

“…The DOS in the spindown part of the Fermi level considerably increases after Zn doping, which is beneficial for increasing the electrical conductivity of the system. 76 Furthermore, the migration energy barriers of NMVP and NMZVP calculated using the CI-NEB method are shown in Figure 7d,e, respectively. The Na 2 migration path reveals that the energy barriers for NMVP and NMZVP are 1.25 and 0.39 eV, respectively, proving that Zn doping can strengthen the Na + diffusion process by reducing the migration energy barriers and improving the ionic conductivity of materials.…”

Heteroatom preintercalated Cl-terminated Ti3C2Tx MXene wrapped with mesoporous Fe2O3 nanospheres for improved sodium ion storage

“…To meet the needs of rapid development of portable electronic devices and electric vehicles, future energy-storage devices are required to possess features of high energy density and superior cycling life. [1][2][3][4] Sodium-ion batteries (SIBs) have recently been thought of as potential candidates because of their abundance and low-cost relative to lithium-ion batteries (LIBs). 5 Unfortunately, the radius of the sodium ion (1.02 Å) is much bigger than that of the lithium ion (0.76 Å), 6 which leads to the failed use of the commercial LIB anode material graphite.…”