Scalable 18650 Cylindrical Cells of Lithium Metal Batteries Using Ni-Rich Cathode with Electrolyte Engineering

Abstract

Li-ion batteries are approaching their theoretical limits in energy densities, motivating the revival of Li metal chemistry. Nevertheless, uncontrollable side reaction forms a chemically unstable SEI and non-uniform Li diffusion through the surface of Li anode, leading to dendritic growth. These instability and safety issues have been the main challenges of lithium metal batteries. To overcome these drawbacks, tremendous efforts have been devoted to the use of artificial solid electrolyte interphase (ASEI) engineering, lithium hosts & scaffolding, and electrolyte additives. However, the electrolyte engineering in 18650 cylindrical lithium metal cells under the practical condition, for instance, the utilization of high cathode loading (>3.5 mAh/cm2), thin lithium metal (e.g., <50 um), and lean electrolyte (<3 g/Ah)) has not been investigated yet. Herein, the first-scalable 18650 lithium metal battery in high Ni content (>88%) NCA cathode with state-of-the-art electrolytes including fluorinated solvent, and flame-retardant additives were studied. The effect of electrolytes at the positive electrode on the active mass loss and lattice volume changes, charge transfer resistance growth, SEI/CEI composition, and lithium dendrite morphology has also been investigated by the post-mortem analysis. To achieve fundamental understanding, reactive molecular dynamic simulation (Reaxff) has been used to investigate the mechanism and compositions of the passivation layer compounds at the lithium anode. The predicted compounds have a correlation to experimental results and the cell performances in terms of capacity retention and coulombic efficiency. Figure 1