Sandwich-type N-C@CoTe₂@C anode: a stress-buffer nanostructure for stable sodium-ion storage

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Transition metal tellurides (TMTes) offer high volumetric capacity for sodium-ion batteries (SIBs).
• Volume expansion during cycling causes capacity degradation in TMTes, limiting their practical use.
• Developing stable anode materials is crucial for advancing SIB technology.

Purpose of the Study:

• To engineer a stable cobalt ditelluride (CoTe2) anode material for SIBs.
• To mitigate capacity attenuation caused by volumetric strain during sodiation/desodiation.
• To investigate the sodium storage mechanism in the designed material.

Main Methods:

• Fabrication of a "sandwich-type" structure with CoTe2 nanocrystals confined between carbon layers.
• Utilizing porous cellulose-derived fibers as an inner carbon framework.
• Employing polyvinylpyrrolidone (PVP)-derived carbon layers as outer protective shells.
• Characterization using ex situ XRD/TEM and kinetic tests.

Main Results:

• The N-C@CoTe2@C electrode demonstrated exceptional cycling stability over 3000 cycles at 2.0 A g-1.
• Excellent rate capability was achieved, with 113.8 mA h g-1 at 5.0 A g-1.
• A multistep conversion reaction and a dual-model Na-storage process were identified.

Conclusions:

• The carbon confinement strategy effectively suppresses volume change and structural pulverization of CoTe2.
• The developed material exhibits promising long-term cycling stability and rate performance for SIB anodes.
• This approach offers a viable pathway for fabricating cost-effective, high-performance SIB anode materials.