Today most of the portable electronic devices contain Lithium-ion batteries with carbonaceous anode materials such as graphite are the most commonly used in portable electronic devices today.(l) In contrast to that lithium metal (3860 mAhg~(-1)) has a more than ten times higher capacity than graphite (372 mAhg~(-1)). and is already being used in primary batteries.(2) Secondary systems like lithium-sulfur batteries offer further reduced cost factors as elemental sulfur is an abundant source.(3) However, these systems suffer from low recharge ability and safety issues. Hence, improvements on the lithium site would overcome these issues. While being exposed to non-aqueous organic electrolytes, the lithium metal surface reacts and forms a protective layer, the so-called solid electrolyte interphase (SEI). The SEI though is not a homogeneous phase as it differs in composition and width.(4) These differences lead to inhomogeneous current densities during charge and discharge, which can ultimately cause the formation of high surface area lithium (HSAL) during lithium plating (charging).(5) hi the worst case the HSAL lead to dendrites, which are small needles, that grow from the anode towards the cathode, thus resulting in an internal short circuit of the cell.(6) These dendrites can also loose contact to the anode and end up as "dead lithium", which results in irreversible capacity loss. As the growth of dendrites corresponds to the current density, efforts have been made to lower the dendrite growth by increasing the accessible lithium surface area, for instance, by using coated lithium powder electrodes (CLiP).(7) Another method of surface alteration is micro-needle modification, where the surface of the lithium metal can be modified easily. This is done simply by rolling it over the lithium surface, thus leaving it with a number of small indentations, which not only increase the accessible surface area, but also serve as preferred lithium plating sites.(8) As the lithium dissolution (stripping) and deposition (plating) at the lithium anode are characterized by overpotentials, previous studies have developed an in situ observation method for HSAL formation, which is used in this work as well.(9)
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