Local Investigations into the Nucleation and Growth of Lithium Dendrites using Scanning Probe Microscopy

Campbell, Colin Thomas

doi:https://doi.org/10.21985/n2-20p3-ev66

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Local Investigations into the Nucleation and Growth of Lithium Dendrites using Scanning Probe Microscopy

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There is considerable technical interest in the improvement of battery technology, as it would allow for the enhancement and realization of many different applications, including the continued miniaturization of portable computational devices, plug-in electric vehicles, and intermittent power storage. Lithium metal represents a theoretical limit on the anode energy density of lithium-ion batteries, currently being considered for many of the aforementioned applications due for their relatively high power and energy density, however lithium metal is not used in rechargeable (“secondary”) batteries because it has the tendency to form dendrites that compromise the stability and rechargeability of the batteries in question. The currently used alternative lithium-ion anode, graphite, entails a modestly reduced cell voltage and approximately one tenth of the specific capacity (charge stored per unit mass of electrode material) compared with Li metal. In this thesis, several behaviors of lithium metal battery-relevant materials are examined, and where applicable, the effects of cycling are examined in the low-current limit. Dendrite formation at higher current is relatively well understood in terms of electrolyte depletion leading to large deposition overpotential and nonuniform/inhomogeneous deposition as a result. Using highly local methods, such as those of Scanning Probe Microscopy, investigations of dendrite nucleation and the elucidation of local properties of battery materials that promote dendrite formation on relevant length scales have been performed. These experiments have previously been highly challenging to perform and examine in battery-relevant conditions over a significant area. The understanding of these properties and the impact they have on dendrite formation will inform future attempts at battery design not just with lithium metal, but with other battery chemistries that can result in dendrite nucleation under applied electric field.

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