Measurement of concentration boundary layer thickness development during lithium electrodeposition onto a lithium metal cathode in propylene carbonate

Li metal was electrodeposited galvanostatically on aLi metal substrate in propylene carbonate (PC) containing 0.5 M lithium perchlorate (LiClO4). The concentration profile of Li+ ion developed with electrodeposition was measured in situ by holographic interferometry. The interference fringe shift at a higher current density indicates that the mass transfer rate of Li+ ion along a vertical cathode is primarily governed by natural convection induced by Li metal electrodeposition. This transient natural convection is reasonably described by the boundary layer theory. However, no interference fringe shift was observed in the initial stage of electrodeposition at a lower current density. The incubation period until the interference fringes start to shift was considerably prolonged as the applied current density was decreased. The charge consumed during the incubation period varied from 7 to 30 mC cm−2. This phenomenon was attributed to the diffusion of residual H2O in the PC electrolyte.