Nanotechnology

Electrode

Sodium sulfide

Sulfide

Anode

Composite number

Nanorod

Engineering

Intercalation (chemistry)

Carbon fibers

X-ray photoelectron spectroscopy

Physical chemistry

Composite material

Inorganic chemistry

Chemistry

Metallurgy

Materials science

Electrolyte

Chemical engineering

ACS Sustainable Chemistry & Engineering

Different from the ion intercalation/deintercalation, conversion-based reactions are a promising way to achieve high capacity of storage materials. However, their too much volume change and poor reversibility during discharge/charge are stubborn to overcome. Herein, by combining hydrothermal synthesis and chemical vapor deposition, a Co9S8 nanorod encapsulated by a N-doped carbon shell (r-Co9S8@NC) is built and applied as an anode material for sodium-ion batteries. Benefiting from the advantages of the chamber-confined conversion and sodiophilic interface offered by the N-doped carbon shell, the Co9S8 redox was well restrained in the shell with improved kinetics, which can not only alleviate the Co9S8/electrolyte side reaction and suppress the large volume expansion and aggregation of Co9S8 nanorods but also enhance the sodium storage/diffusion ability. As expected, the r-Co9S8@NC electrodes exhibit a high capacity of 675 mAh g–1 at 50 mA g–1, an excellent rate capability (342 mAh g–1 at 10 A g–1), and a good cycling stability (317 mAh g–1 after 1500 cycles at 5 A g–1 and 483 mAh g–1 after 150 cycles at 500 mA g–1) among which the rate capability is outperforming most of the reported metal-sulfide-based anodes. Further, the sodium storage mechanism and the good reversibility of the r-Co9S8@NC electrode have been revealed and confirmed by the XRD and XPS characterizations. This work provides an effective strategy to design storage materials based on a chamber-confined conversion reaction.

A Sodium Storage Material Based on Chamber-Confined Conversion of Co<sub>9</sub>S<sub>8</sub> Nanorod Encapsulated by N-Doped Carbon Shell

A Sodium Storage Material Based on Chamber-Confined Conversion of Co9S8 Nanorod Encapsulated by N-Doped Carbon Shell

A Sodium Storage Material Based on Chamber-Confined Conversion of Co₉S₈ Nanorod Encapsulated by N-Doped Carbon Shell