In this work, the usage of the scanning droplet cell system (SDS) as high-throughput technique for non-aqueous Li-based batteries research is explored. The SDS is an advanced electrochemical device that has been used in fields of electrochemistry such as electrocatalysis and corrosion. The working principle is based on the confinement of the electrolyte together with a reference and a counter electrode inside a miniaturized electrochemical cell called head of the SDS, which is fixed on a X-, Y-, Z-stepper motor and is pressed onto the sample surface, which acts as working electrode. Only the area in contact with the electrolyte confined by the miniaturised SDS is electrochemically active so that the electrochemical reactions are spatially localized at this specific spot of the sample surface. This permits the automatization to carry out a large number of non-supervised experiments, optimizing resources and minimizing human error. This methodology has been mainly explored in aqueous systems, with oxygen and water-containing environments. However, the traces of water or oxygen contamination of the Li-ion batteries electrolyte lead to the appearance of undesired electrochemical side reactions due to the large operating voltage of Li-ion battery cells (3.7 V) and the limited electrochemical stability window of water (1.23 V). Therefore, research on Li-ion batteries requires the use of an Ar-filled glovebox, which excludes water and oxygen.

Our first aim of this work was to install the SDS inside an Ar-filled glovebox, performing the necessaries adaptations to the SDS to be suitable for the investigation of high-energy Li-based batteries. Such adaptations were no limited to placing the SDS system inside an Ar-filled glovebox, but they included specific connections, the use of the materials compatible with organic solvents, etc. Once the SDS was installed under ambient conditions, two cases of studies were investigated to show the benefits of the automatized SDS in non-aqueous battery research.

On the one hand, the Li plating efficiency, which is of key importance for the practical implementation of high-energy Li metal batteries (post Li-ion battery technology), was investigated. In this case, the influence of pulsed Li plating protocols on the coulombic efficiency was evaluated by programming the SDS system to conduct automatically pulsed/continuous Li plating protocols followed by continuous Li stripping process automatically. The results showed that fine-tuning of the parameters of pulsed Li plating protocols, i. e. the relaxation period and Li plating duration is required to improve Li plating efficiencies at high current densities.

On the other hand, a novel redox-mediated SDS operating mode has been developed to study the properties and defects on the solid-electrolyte interface (SEI). SEI nanolayer is a protecting layer formed on the surface of the negative electrode due to the electrochemical decomposition of carbonate-based electrolyte. This layer must not permit electron transfer from the electrode to the electrolyte (high electrical resistivity), preventing continuous decomposition of electrolyte, but it must have a good ionic conductivity (high ionic conductivity) permitting the movement of Li cations through it. These properties are of key importance for the Li-ion battery performance. The evaluation of the charge transfer kinetics of the redox mediator through the SEI were conducted using cyclic voltammetry and EIS analysis using methyl viologen dichloride as redox-mediator. The results obtained by the EIS study were similar to those obtained by means of CV, demonstrating the feasibility of the redox-mediated SDS for the study of the SEI properties (attached Figure).