Understanding of Lithium Insertion into 3D Porous Carbon Scaffolds with Hybridized Lithiophobic and Lithiophilic Surfaces by In-Operando Study

In-operando study coupled with voltage/current profiles are presented in order to unveil lithium insertion processes into 3D porous carbon nanotube (CNT) structures whose surfaces were altered to have lithiophobic, lithiophilic, and hybridized lithiophobic/philic characteristics using graphitic surfaces with/without carboxyl/hydroxyl groups. We found the lithiophobic graphitic surfaces hindered lithium insertion into the scaffold despite the high conductivity of CNT. The lithiophilic surface caused another problem of lithium deposition on the outer surface of the electrode, clogging pores and engendering dendrites. Conversely, in the hybridized CNT, lithiophilic trenches partially created on the pristine CNT allowed for uniform lithium deposition into the pores by simultaneously improved lithium attraction and charge transfer, reaching a high areal capacity of 16 mAh cm–2 even with a current density of 8 mA cm–2 without noticeable dendrite formation and volume expansion. Our hybridization approach provides valuable insight to realize a high-energy-density anode by uniformly impregnating lithium into porous media.