The Fabrication of in Situ Polymerization of 1,3-Dioxlane/Poly(vinyl alcohol)/Polyethylenimine Quasi-Solid Polymer Electrolyte for a Lithium Metal Battery Operated at Low Temperatures

The development of a high-performance electrolyte that can work at low temperatures is critical for expanding the application of lithium metal batteries. However, most of the present electrolytes suffer from low ionic conductivity and poor interface contact at low temperatures. Herein, an ∼21 μm-thick quasi-solid polymer electrolyte is prepared by in situ polymerization of 1,3-dioxlane (PDOL) within the poly(vinyl alcohol)/polyethylenimine (PVA/PEI) nanofiber skeleton that contains −NH– groups. The generated hydrogen bond interactions between PDOL and PVA/PEI nanofiber, together with the inherently strong mechanical strength of the nanofiber, confer quasi-solid polymer electrolyte (QSE@PVA/PEI) the tensile strength of 12.1 MPa. Meanwhile, the interactions also interfere with the chain arrangement of PDOL and efficiently enhance the chain mobility, giving QSE@PVA/PEI a remarkable ionic conductivity of 3.29 × 10–5 S cm–1 and a high Li+ transference number of 0.437 at −60 °C. As a result, the Li/QSE@PVA/PEI/Li cell can operate over 1500 h without obvious polarization at 0.2 mA cm–2 and −20 °C. Moreover, the NCM523/QSE@PVA/PEI/Li cell can stably cycle at −20 °C, delivering a high discharge capacity of 106.7 mAh g–1 over 600 cycles at 0.2 C, which outperforms most reported electrolytes. Even at −40 °C, a modest discharge capacity of 75.2 mAh g–1 is obtained at 0.2 C.