(Invited) Mechanical and Chemical Surface Modification of Lithium As a Tool to Alter the Electrodeposition Process and to Improve the Cycling Performances of Lithium-Metal Electrodes
Authors: Stan Marian Cristian , Becking Jens , Kolek Martin , Groebmeyer Albert , Bieker Peter , Winter Martin 
Published: February 2020

Driven by the demand of higher energy density batteries, systems based on sulfur and oxygen as cathode materials with lithium electrode regained increased interest as successful candidates for beyond lithium-ion systems [1,2]. Nevertheless, at the surface of the lithium electrode the existence of a native surface film and the formation of a solid electrolyte interphase (SEI) leads to a heterogeneous electrodeposition and thus inhomogeneous current densities during the discharge and charge process. Ultimately, this will result in the formation of high surface area lithium (HSAL, during electrodeposition) and hole/pit formation (during electrodissolution) [3]. Therefore, lithium electrodes are mainly characterized by poor cycling performance with low Coulombic efficiencies, continuously loss of active material that arises in safety concerns.
For practical applications, the electrode-electrolyte interface needs to be tuned in order to avoid these barriers and to reduce the product costs [4]. Previously we have shown that controlling the chemical composition and morphology of the lithium-electrode surface by thinning the surface native film, improved cycling performances with low overpotentials of the lithium electrodeposition was obtained [5]. Furthermore, we would like to further expand such method of mechanically pre-treated lithium electrodes, by creating an artificial-SEI through dry and solution based methods [6]. In this way, it is possible to homogenize the flux of Li+ during the electrodeposition process resulting in stabilized electrochemical performances. Furthermore, we would like to present that such surface modification avoids also the formation of the hole/pits thus reduces the formation of the HSAL. Finally, these surface modifications can be successfully transferred to thin lithium electrodes (<30 µm) as the nominal capacities used with the common laboratory grade lithium electrodes (>150 µm) are extremely oversized. These demonstrations will present the strength of the above mentioned approaches to further improve the electrochemical performances through the interface engineering of lithium electrodes.
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