Microwave-Assisted Expanded Graphite as a Long Cyclic Cathode for the Lithium Dual-Ion Battery.

Lithium metal (Li) has been recognized as a promising anode for most energy storage devices, owing to its high theoretical capacity. Nevertheless, Li anode present serious safety hazards and have a rapidly fading capacity, which limits its practical applications. Herein, a lithium-expanded graphite dual-ion battery (Li-EG DIB) was developed by combining a Li metal sheet as an anode with expanded graphite (EG) as a cathode. EG was produced by microwave (MW) photons energy (~1 × 10-5 eV) at different time durations (15, 30, 45, and 60 s) to allow moderate expansion between the graphite sheets and the removal of the surface functional groups that encourage the intercalation and de-intercalation of the ions; consequently, the capacity was improved. The MW-EG samples were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectrophotometry (FT-IR). The EG synthesized at 45 s in MW exhibited a high capacity and a stable and long cycling life. The charge capacity of the Li-EG-45 DIB after 500 cycles at 0.05 Ag-1 was 20.3 mAh g-1 in the voltage window of 2-5 V. It is worth noting that the EG-45 electrode showed ~100% capacity retention, even after the rate test.