Ordered and Fast Ion Transport of Quasi‐solid‐state Electrolyte with Regulated Coordination Strength for Lithium Metal Batteries

Abstract

AbstractPolymer based quasi‐solid‐state electrolyte (QSE) has attracted great attention due to its assurance for high safety of rechargeable batteries including lithium metal batteries (LMB). However, it faces the issue of low ionic conductivity of electrolyte and solid‐electrolyte‐interface (SEI) layer between QSE and lithium anode. Herein, we firstly demonstrate that the ordered and fast transport of lithium ion (Li+) can be realized in QSE. Due to the higher coordination strength of Li+ on tertiary amine (−NR3) group of polymer network than that on carbonyl (−C=O) group of ester solvent, Li+ can diffuse orderly and quickly on −NR3 of polymer, significantly increasing the ionic conductivity of QSE to 3.69 mS cm−1. Moreover, −NR3 of polymer can induce in situ and uniform generation of Li3N and LiNxOy in SEI. As a result, the Li||NCM811 batteries (50 μm Li foil) with this QSE show an excellent stability of 220 cycles at ≈1.5 mA cm−2, 5 times to those with conventional QSE. LMBs with LiFePO4 can stably run for ≈8300 h. This work demonstrates an attractive concept for improving ionic conductivity of QSE, and also provides an important step for developing advanced LMB with high cycle stability and safety.