Study on the enhancement of the interfacial properties between lithium metal electrode and polymer electrolyte

Abstract

Lithium metal polymer batteries (LMPB) are expected to achieve a high energy density due to a high specific capacity of the lithium metal anode. However, the performance of LMPB was restricted by the following problems. High chemical or electrochemical reactivity of the metallic lithium electrode with the electrolyte leads to the capacity loss by the consumption of electrolyte and the interfacial resistance by the growth of SEI (Solid Electrolyte Interphase) layer. The dendritic lithium, which produces the internal short-circuit of the battery, is also formed due to the non-uniform current distribution of the lithium metal electrode. These problems of the metallic lithium electrode need to be solved for the realization of the lithium metal polymer batteries. Therefore, it is quite important to control the lithium electrode-polymer electrolyte interface. In this study, the ideas for the improvement of electrochemical properties at polymer electrolyte-the metallic lithium electrode interface were proposed and its effects were carefully discussed. The interfacial properties between the gel polymer electrolyte and the lithium metal electrode were strongly dependent on the matrix structure. When the poly(vinylacetate) (PVAc) showing good compatibility with the liquid electrolyte was introduced into the gel polymer electrolyte based on P(VdF-co-HFP), the initial interfacial resistance and the interfacial stability was enhanced owing to the improvement of the physical contact with the lithium metal electrode and the reduction of the leakage behavior of liquid electrolyte from the gel polymer electrolyte. To overcome the deterioration of the mechanical strength for the gel polymer electrolyte by introducing PVAc component, the protective thin layer based on the crosslinked gel polymer electrolyte was designed and introduced on the surface of lithium metal by in-situ photopolymerization. The protective thin layer consisted of the crosslinking agent (1,6-Hexanediol dic...