Rapid Oxidation and Reduction of Lithium for Improved Cycling Performance and Increased Homogeneity

This work enables highly "uniform" and "reversible" deposition of Li metal in carbonate electrolytes through a one-time rapid oxidation and reduction (ROAR) treatment. Over the years, Li metal has been plagued with irreversible dendritic growths that create isolated and unusable structures called "dead Li". Accumulation of dead Li negatively impacts the ion transport, performance, and safety of Li metal batteries. To address this long-standing problem, we have developed an in situ process to uniformly create reversible Li deposits. Our results demonstrate that a combination of high-voltage pulses, which rapidly oxidize and reduce Li in both directions (ROAR treatment), leads to strikingly more homogeneous morphology and eliminates reaction pathway transitions. We validate that ROAR treatments eliminate traditional "mossy dendrites" under extended cycling (<250 cycles) in standard carbonate-based electrolytes. Moreover, ROAR treatments create a 500% reduction in overpotential for electrodissolution/deposition and eliminate "peaking" voltage behavior.

Intrinsic Properties of Individual Inorganic Silicon-Electrolyte Interphase Constituents

Because of the complexity, high reactivity, and continuous evolution of the silicon-electrolyte interphase (SiEI), "individual" constituents of the SiEI were investigated to understand their physical, electrochemical, and mechanical properties. For the analysis of these intrinsic properties, known SiEI components (i.e., SiO₂, Li₂Si₂O₅, Li₂SiO₃, Li₃SiO_x, Li₂O, and LiF) were selected and prepared as amorphous thin films. The chemical composition, purity, morphology, roughness, and thickness of prepared samples were characterized using a variety of analytical techniques. On the basis of subsequent analysis, LiF shows the lowest ionic conductivity and relatively weak, brittle mechanical properties, while lithium silicates demonstrate higher ionic conductivities and greater mechanical hardness. This research establishes a framework for identifying components critical for stabilization of the SiEI, thus enabling rational design of new electrolyte additives and functional binders for the development of next-generation advanced Li-ion batteries utilizing Si anodes.