Abstract:

Owning to sodium’s high abundance, relatively low cost, similar chemical properties to Li and very suitable redox potential of E0(Na+/Na) = -2.71 V versus SHE which is only 0.3 V above that of lithium, rechargeable sodium ion battery hold much promise as potential alternatives to current lithium ion batteries for energy storage applications. Carbon material is regarded as the most promising anode candidate for sodium ion battery. Particularly, carbon nanosheet with porous structure and high conductivity is expected to have improved sodium ion storage properties. In this paper, we present a two-step pyrolysis-based method for facile synthesis of porous carbon nanosheets with high capacity as anode in sodium-ion battery. In this method, sodium chloride was selected as a hard template, nickel nitrate as the metal source and glucose as the carbon source with pyrolysis temperature of 750 °C in nitrogen atmosphere. The first obtained is Ni-incorporated carbon nanosheets which were refluxed with dilute hydrochloric acid to produce uniform porous carbon nanosheets. TEM images shows that the pores in the as-prepared porous nanosheets spread evenly with narrow-distributed diameter; Raman spectra indicate that the graphitic degree of the product decreases after acid treatment; BET results demonstrate that the specific surface area can reach 340 m²•g^-1; Electrochemical characterization says that the as-prepared porous nanosheets have excellent Na⁺ storage rate capability of 173 mAh•g^-1 at 1000 mAh•g^-1 and exhibit outstanding cycle stability at 100 mA•g^-1 with 309.4 mAh•g^-1 capacity even after 200-cycle running. The super sodium ion storage performance of the produced carbon nanosheets could be attributed to the specific structure, where the interconnected micro- and meso-pores inside minimized the diffusion lengths and the 2D carbon nanosheet structure enhanced electronic conductivity. These results show that the porous carbon nanosheet is a promising anode material for sodium ion batteries.

Key words: porous carbon nanosheet, pyrolysis, anode material, sodium ion batteries