Polymer Protective Layer Releasing Additives to Electrolyte of Lithium Metal Anode

Abstract

As the need of batteries with high energy density raises, lithium metal anode has attracted considerable attention due to its high theoretical specific capacity and low reduction potential. However, there are several technical issues in practical use of lithium metal anode due to the growth of lithium dendrite and chemical instability with liquid electrolyte. It is essential to form the stable solid electrolyte interphase (SEI) layer on lithium metal anode to prevent lithium dendrite growth and minimize side reaction of liquid electrolyte. Designing the SEI with high Li+ ion conductivity and mechanical strength is imperative to stabilize lithium metal anode. Recently, various additives have been investigated to form a stable SEI layer on Li metal. However, during repetitive charge and discharge process, the additives in the electrolyte can be depleted by continuously forming SEI, which results in capacity fading of batteries. In this work, we developed the polymer protection layer containing excessive amount of additives that form the stable SEI layer. The additives can be stored in the polymeric layer, continuously released to the electrolyte during the repeated cycling. Electrochemical analyses such as linear sweep voltammetry and cyclic voltammetry were investigated, and the Li/Li symmetric cells showed the regulation of lithium deposition with small overpotential. The cycling performance of lithium metal batteries with protection layer was evaluated with high nickel NCM cathode.