Poly(2-aminoazulene) Filler–Improved PEO-Based Electrolyte for Highly Stable Solid-State Li-Metal Batteries

Abstract

Poly(ethylene oxide) (PEO) is regarded as an attractive solid-state electrolyte in lithium-ion batteries (LIBs). However, relatively low ionic conductivity of pristine PEO is a critical bottleneck to boost high-performance solid-state LIBs. Herein, poly(2-aminoazulene) (PAAz) was synthesized using the oxidation polymerization strategy and acted as a polymeric filler in the fabrication of PEO−PAAz composite electrolyte. Compared with PEO electrolyte, the composite electrolyte had a better ionic conductivity (9.27 × 10−6 vs 6.47 × 10−5 S cm−1 at 30 °C), Li+ transference number (0.21 vs 0.51), and suppression of Li dendrites. Consequently, the PEO−PAAz electrolyte paired Li/LiFePO4 cell had a high capacity (156 mAh g−1 at 0.5 C, 1 C = 170 mA g−1) and stability (only 8% capacity loss after 300 cycles); these are better than those of the PEO-based cell (132 mAh g−1, 45% capacity loss). In addition, the PEO−PAAz-based cell could run for 1200 cycles with 60% capacity retention at 1 C. This study provides both a new organic filler for PEO-based solid-state LIBs and a method of improving the performance of solid-state LIBs, especially in terms of a long lifetime.