Effect of nano Al2O3 addition on cycling performance of poly(ether block amide) based solid-state lithium metal batteries

Abstract

A novel poly(ether block amide) (PEBA) based solid-state polymer electrolyte (SPE) was prepared using a casting method, in which 20wt% lithium (Li) bis-(trifluoromethanesulfonyl)imide (LiTFSI) and aluminum oxide (Al2O3) nanoparticles were used as the Li salt and solid plasticizer, respectively. In the case of addition of 3wt% Al2O3 nanoparticles, ion conductivity of the obtained PEBA 2533–20wt% LiTFSI-3wt% Al2O3 SPE was 3.57 × 10−5 S cm−1 at 25 °C. Furthermore, the Li symmetrical battery assembled with it showed excellent cycling stability (1000 h) at 0.1 mA cm−2. While, the assembled all-solid-state Li/PEBA 2533–20% LiTFSI-3wt% Al2O3/LiFePO4 (areal capacity: 0.15 mAh cm−2) battery maintained 94.9% of the maximal capacity (133.9 mAh g−1@0.1 mA cm−2) at 60 °C even after 650 cycles with a superior average coulombic efficiency (CE) of 99.84%. By using X-ray photoelectron spectroscope (XPS), self-aggregation layer (SAL) of polyamide 12 (PA12) of PEBA 2533 was discovered, which should contribute to promoting the robustness of lithium fluoride (LiF) enriched solid-electrolyte interphase (SEI) layer. In addition, it is considered that the state of interface between SPE and cathode should be the cause of voltage polarization of the full cell.