Physics

Meteorology

Nanotechnology

Electrode

Carbon nanofiber

Coating

Energy storage

Anode

Composite number

Engineering

Conductivity

Carbon fibers

Physical chemistry

Nanoparticle

Composite material

Power (physics)

Chemistry

Materials science

Diffusion barrier

Layer (electronics)

Graphene

Quantum mechanics

Atmospheric temperature range

Chemical engineering

Carbon nanotube

Electrochemistry

Small

Developing low cost, long life, and high capacity rechargeable batteries is a critical factor towards developing next-generation energy storage devices for practical applications. Therefore, a simple method to prepare graphene-coated FeS2 embedded in carbon nanofibers is employed; the double protection from graphene coating and carbon fibers ensures high reversibility of FeS2 during sodiation/desodiation and improved conductivity, resulting in high rate capacity and long-term life for Na+ (305.5 mAh g-1 at 3 A g-1 after 2450 cycles) and K+ (120 mAh g-1 at 1 A g-1 after 680 cycles) storage at room temperature. Benefitting from the enhanced conductivity and protection on graphene-encapsulated FeS2 nanoparticles, the composites exhibit excellent electrochemical performance under low temperature (0 and -20 °C), and temperature tolerance with stable capacity as sodium-ion half-cells. The Na-ion full-cells based on the above composites and Na3 V2 (PO4 )3 can afford reversible capacity of 95 mAh g-1 at room temperature. Furthermore, the full-cells deliver promising discharge capacity (50 mAh g-1 at 0 °C, 43 mAh g-1 at -20 °C) and high energy density at low temperatures. Density functional theory calculations imply that graphene coating can effectively decrease the Na+ diffusion barrier between FeS2 and graphene heterointerface and promote the reversibility of Na+ storage in FeS2 , resulting in advanced Na+ storage properties.

Graphene‐Encapsulated FeS2 in Carbon Fibers as High Reversible Anodes for Na+/K+ Batteries in a Wide Temperature Range