Design and fabrication of polypyrrole/expanded graphite 3D interlayer nanohybrids towards high capacitive performance

Abstract

Polypyrrole/expanded graphite (PPy/EG) nanohybrids, with a hierarchical structure of a three dimensional EG framework with a thick PPy coating layer, have been synthesized via a vacuum-assisted intercalation in situ oxidation polymerization method. In the synthesis, pyrrole monomers were intercalated into the irregular pores of EG with the assistance of a vacuum pump. Subsequently, the intercalated pyrrole monomers assembled on both sides of the EG nanosheets and formed PPy by an in situ polymerization method. As electrode materials, the typical PPy/EG10 sample with an EG content of 10% had a high specific capacitance of 454.3 F g⁻¹ and 442.7 F g⁻¹ (1.0 A g⁻¹), and specific capacitance retention rate of 75.9% and 73.3% (15.0 A g⁻¹) in 1 M H₂SO₄ and 1 M KCl electrolytes, respectively. The two-electrode symmetric supercapacitor showed a high energy density of 47.5 W h kg⁻¹ at a power density of 1 kW kg⁻¹, and could retain superb stability after 2000 cycles. The unique self-supporting structure feature and homogeneous PPy nanosphere coating combined the contributions of electrochemical double layer capacitance and pseudo-capacitance, which made the nanohybrids an excellent electrode material for high performance energy storage devices.