Improvement of Li metal-electrolyte interfacial stability in carbonate electrolyte

Abstract

As the application of a battery develops from small mobile device to medium and large vehicle battery, the demand for high energy battery increased. Among the next-generation batteries, the lithium metal anode, which is in the spotlight, has a high specific capacity and a low working voltage. Due to these advantages, when combined with high-nickel positive electrode, lithium metal electrode can effectively ensure a high energy system. However, continuous cycling of lithium metal cause dendritic growth, which results in additional electrolyte decomposition and internal short circuits. While ether-based electrolyte has been proposed prevent additional side reaction at Li metal-electrolyte interfacial, it is challenging to apply it to a high energy system that is a practical purpose of a lithium metal battery (LMB). Because of this issue, there is a renewed focus on carbonate-based electrolyte. However, in the case of a carbonate- based electrolyte, the instability on Li metal-electrolyte interfacial lead to severe dendritic lithium formation and electrolyte decomposition, resulting in a rapid capacity degradation. In this study, I will discuss to stepwise modulation carbonate electrolyte to improvement of Li metal-electrolyte interfacial stability. First, thermodynamic modulation controls to upstream the reduction potential stable window of carbonate-based electrolyte. Through structure change from cis-cis DMC to cis-trans DMC, LUMO energy is positively shift. The polar conformer, which is cis-trans DMC improves to reduction stability on the lithium metal surface. Second, since improving the reduction stability of electrolyte does not lead to changes in components of the SEI, kinetic modulation of introduction an azamacrocyclic ligand serves to enhance the solubility of LiNO3, which forms a Li3N-based SEI. By forming SEI layer, nitrate anion acts as a cation shield of an azamacrocyclic ligand bonded to lithium to suppress morphology. As a result, a stable lithium-electrolyte interfacial is ensured through stepwise improvement of a carbonate electrolyte, improving cycle performances of a high energy LMB system.