Neil Dasgupta1
University of Michigan1
Solid-state batteries (SSB) have seen a dramatic increase in research in recent years because of their ability to address safety challenges associated with flammable liquid electrolytes, and the potential to enable Li metal anodes. Recently there has been an increase in attention paid to anode-free SSB configurations, where all of the lithium inventory in the battery is supplied from the cathode. Accordingly, Li metal is plated out at the interface between a solid electrolyte and a metallic current collector. This enables a N:P ratio of 1, representing a significant increase in the theoretical energy density compared to cells with excess Li metal in the anode. The anode-free configuration unique physical phenomena with regards to chemo-mechanics at the interface, and also represents a valuable platform to quantify the stability and reversibility of Li plating and stripping at solid-solid interfaces.<br/> <br/>To probe the dynamic evolution of anode-free solid-state batteries, in this talk, I will present results using a complimentary set of <i>in situ/operando</i> methodologies. First, we will explore quantify the impacts of electrochemical cycling conditions and external variables on the voltage signatures and reversibility of anode formation. Comparisons will be made between anode-free cells using state-of-the-art metal oxide and sulfide solid electrolytes. <i>Operando</i> video microscopy will be used to study the morphological evolution of the interface, including 3-dimensional analysis using focus variation microscopy. The chemical evolution of SEI formation during the initial anode formation cycle will be explored using <i>operando</i> x-ray photoelectron spectroscopy (XPS). The results of these investigations point towards unique processes that occur in anode-free SSBs, including transitions in reaction pathways between SEI formation and Li plating, as well as mechanical evolution of both the Li metal and current collector during nucleation and growth.