High-intensity ultrasonication as a way to prepare graphene/amorphous iron oxyhydroxide hybrid electrode with high capacity in lithium battery

• Ultrasound-assisted preparation of graphene/FeOOH hybrid material.
• Small particle size, amorphous character and high dispersion is achieved by high-intensity ultrasonication.
• Anchoring of iron ions to graphene evaluated by electron paramagnetic resonance.
• Enhancement of the electrochemical behavior in lithium batteries.

The preparation of graphene/iron oxyhydroxide hybrid electrode material with very homogeneous distribution and close contact of graphene and amorphous iron oxyhydroxide nanoparticles has been achieved by using high-intensity ultrasonication. Due to the negative charge of the graphene surface, iron ions are attracted toward the surface of dispersed graphene, according to the zeta potential measurements. The anchoring of the FeO(OH) particles to the graphene layers has been revealed by using mainly TEM, XPS and EPR. TEM observations show that the size of the iron oxide particles is about 4 nm. The ultrasonication treatment is the key parameter to achieve small particle size in these graphene/iron oxyhydroxide hybrid materials. The electrochemical behavior of composite graphene/amorphous iron oxyhydroxide prepared by using high-intensity ultrasonication is outstanding in terms of gravimetric capacity and cycling stability, particularly when metallic foam is used as both the substrate and current collector. The XRD-amorphous character of iron oxyhydroxide in the hybrid electrode material and the small particle size contribute to achieve the improved electrochemical performance.