Towards high rate Li metal anodes: Enhanced performance at high current density in a superconcentrated ionic liquid

Although high energy density and fast charging rates are vital for future advanced battery applications such as electric vehicles (EVs), the impact of fast charge rates is not widely investigated for key technologies such as those based on lithium metal. Here, for the first time, Li metal deposition/dissolution in a superconcentrated ionic liquid (IL) is demonstrated at the high current densities necessary for fast charge technologies. Operation at high current is shown to enhance the cycling efficiency from 64 ± 3% at 1 mA cm-2 up to 96 ± 1% at 20 mA cm-2 on a bare Ni substrate, providing a new path to enable these technologies. XPS, ToF-SIMS and SEM measurements revealed that a stable and LiF-dominated SEI, favourable nucleation and compact dendrite-free Li morphology enabled enhanced cycling efficiency at higher currents.