Hierarchical carbon framework wrapped Na3 V2 (PO4 )3 (HCF-NVP) is successfully synthesized through chemical vapor deposition on pure Na3 V2 (PO4 )3 particles. Electrochemical experiments show that the HCF-NVP electrode can deliver a large reversible capacity (115 mA h g(-1) at 0.2 C), superior high-rate rate capability (38 mA h g(-1) at 500 C), and ultra-long cycling stability (54% capacity retention after 20 000 cycles).

Hard carbon is regarded as the most promising anode material for commercialization of Na ion batteries because of its high capacity and low cost. At present, the practical utilization of hard carbon anodes is largely limited by the low initial Coulombic efficiency (ICE). Na ions have been found to adopt an adsorption–insertion storage mechanism. In this paper a systematic way to control the defect concentration and porosity of hard carbon with similar overall architectures is shown. This study elucidates that the defects in the graphite layers are directly related to the ICE as they would trap Na ions and create a repulsive electric field for other Na ions so as to shorten the low‐voltage intercalation capacity. The obtained low defect and porosity hard carbon electrode has achieved the highest ICE of 86.1% (94.5% for pure hard carbon material by subtracting that of the conductive carbon black), reversible capacity of 361 mA h g−1, and excellent cycle stability (93.4% of capacity retention over 100 cycles). This result sheds light on feasible design principles for high performance Na storage hard carbon: suitable carbon layer distance and defect free graphitic layers.

Electrode materials based on electrochemical conversion reactions have received considerable interest for high capacity anodes of sodium-ion batteries. However, their practical application is greatly hindered by the poor rate capability and rapid capacity fading. Tuning the structure at nanoscale and increasing the conductivity of these anode materials are two effective strategies to address these issues. Herein, a two-step ion-exchange method is developed to synthesize hierarchical Cu-doped CoSe microboxes assembled by ultrathin nanosheets using Co-Co Prussian blue analogue microcubes as the starting material. Benefitting from the structural and compositional advantages, these Cu-doped CoSe microboxes with improved conductivity exhibit enhanced sodium storage properties in terms of good rate capability and excellent cycling performance.

FePO4 nanospheres are synthesized successfully through a simple chemically induced precipitation method. The nanospheres present a mesoporous amorphous structure. Electrochemical experiments show that the FePO4/C electrode demonstrates a high initial discharging capacity of 151 mAh g(-1) at 20 mA g(-1), stable cyclablilty (94% capacity retention ratio over 160 cycles), as well as high rate capability (44 mAh g(-1) at 1000 mA g(-1)) for Na-ion storage. The superior electrochemical performance of the FePO4/C nanocomposite is due to its particular mesoporous amorphous structure and close contact with the carbon framework, which significantly improve the ionic and electronic transport and intercalation kinetics of Na ions.

Sodium-ion batteries (SIBs) have attracted enormous attention as an alternative to lithium-ion batteries (LIBs). Recent studies on SIB cathodes have demonstrated performances comparable with their LIB counterparts. One major challenge for SIBs thus resides in exploiting suitable anode materials. Here, we develop a multistep templating method to confine SnS 2 nanosheets in different carbon hollow structures including nanotubes, nanoboxes, and hollow nanospheres. Benefiting from their unique structural merits, these SnS 2 -carbon nanohybrids manifest excellent sodium storage properties.