Stable Li metal anode by a polyvinyl alcohol protection layer via modifying solid-electrolyte interphase layer

Abstract

Lithium (Li) metal is considered an ideal anode for next-generation high energy Li metal batteries (LMBs) due to its high theoretical specific capacity and low electrochemical potential. However, stable cycling of LMBs has long been restrained by the extremely unstable interfaces between the Li metal anode and liquid electrolyte. Here, we found that low-cost polyvinyl alcohol (PVA) polymer can be applied as an effective protection layer for Li metal anodes in both ether- and carbonate-based electrolytes. The PVA protection layer will participate in and facilitate formation of a superior PVA-modified solid electrolyte interphase (SEI) layer on Li metal, leading to uniform deposition of Li and alleviated consumption of electrolyte. Li||Cu half-cells with the PVA protection layers show dendrite-free Li deposition and greatly extended stable cycling with high Coulombic efficiency (CE) (e.g. average CE of 98.3% for over 630 cycles). Li-Sulfur, Li–LiFePO4 and Li–LiNi0.6Co0.2Mn0.2O2 full-cells using the PVA-protected Li metal anodes also show significantly improved electrochemical performance with better capacity retention and higher CE, even under lean electrolyte (7.5 μL mAh−1) condition.