A new insight into Li-staging, in-situ electrochemical exfoliation, and superior Li storage characteristics of highly crystalline few-layered graphene

Abstract

Highly crystalline few-layered graphene (hcFLG) is synthesized using microwave exfoliation of in-house prepared graphene oxide. When hcFLG is tested as an anode material in a Li-ion coin cell, it showed unique lithiation electrochemistry. Cyclic voltammetry (CV), structural and electrochemical impedance spectroscopic analyses of hcFLG showed enhanced surface lithiation above 0.3 V and in-situ exfoliation of hcFLG responsible for excellent storage capacity of hCFLG. Below 0.3 V, the CV data before and after long-term cycling showed a unique Li-staging phenomenon and confirmed that diffusion-controlled lithiation is responsible for stable capacity. hcFLG delivered reversible specific capacities as high as 400 and 330 mAh/g at current rates of 0.1 and 1 C, respectively. hcFLG also exhibited an excellent rate capability by showing a reversible specific capacity of 215 mAh/g at a very high current rate of 10 C. At the end of long-term cycling (i.e., 1175 cycles), hcFLG displayed a significant increase in specific capacity from 330 to 555 mAh/g and 200 to 365 mAh/g at current rates of 1.0 and 2.0 C, respectively, attributed to a safe in-situ exfoliation. The performance of hcFLG is far superior to the commercial graphite and other materials of the same class. hcFLG is best suited for emerging battery technologies like ‘All Graphene Battery”.