A Polymer Scaffold Binder Structure for Improving Long-Term Cycle Performance of Lithium Metal Powder Electrode

Abstract

Lithium metal anode is being revalued as a candidate for large-scale battery systems, such as electric vehicles (EVs) and energy storage systems (ESSs), owing to its high theoretical density and lowest negative potential. However, to commercialize lithium metal in large-scale battery systems, the formation of dendrite and continuous side reactions during repeated cycling must be suppressed. In our previous contribution, we improved this problem by using Li metal powder (LiMP), which was compressed on a Cu foil with a small amount of binder instead of bare lithium metal foil. Due to higher surface area of LiMP, the actual current density felt by LiMP is much lower than that of general lithium foil. Nevertheless, during repeated cycling, the high-surface-area structure of LiMP became flatter and is finally covered with numerous dendrites. Herein, we report a LiMP electrode with a scaffold barrier using polyimide (PI) binder. As PI binder forms its own barrier structure at the interstitial region between LiMP particles, the energy density of the cell can be enhanced without additional hosting materials or processes. Especially, the scaffold structure of PI binder can confine the Li stripping/plating reactions within the matrix. Furthermore, we investigated their electrochemical properties, such as DC-IR based on hybrid pulse power characterization (HPPC), cycle performance, and Li plating/stripping mechanism.