Three-dimensional polyimide nanofiber framework reinforced polymer electrolyte for all-solid-state lithium metal battery.

The replacement of traditional liquid electrolytes with polyethylene oxide (PEO) based composite polymer electrolytes (CPEs) is an important strategy to address the current flammability and explosiveness of lithium batteries since PEO CPEs have high flexibility, excellent processability and moderate cost. However, the insufficient ionic conductivity and inferior mechanical strength of PEO CPEs do not suit the operating requirements of all-solid-state lithium metal batteries at room temperature. Herein, three-dimensional (3D) framework composed of interweaved high-modulus polyimide (PI) nanofibers along with functional succinonitrile (SN) plasticizers are employed to synergistically reinforce the ionic conductivity and mechanical strength of PEO CPEs. Impressively, benefitting from the synergistic effects of 3D PI framework and SN plasticizer, PI-PEO-SN CPEs exhibits high ionic conductivity of 1.03 × 10-4 S cm-1 at 30 °C, remarkable tensile strength of 4.52 MPa, and superior Li dendrites blocking ability (>400 h at 0.1 mA cm-2). Such favorable features of PI-PEO-SN CPEs endow LiFePO4/PI-PEO-SN/Li solid-state prototype cells with high specific capacity (151.2 mA h g-1 at 0.2 C), long cycling lifespan (>150 cycles with 91.7 % capacity retention), and superior operating safety even under bending, folding and cutting harsh conditions. This work will pave the avenues to design and fabricate new high-performance PEO CPEs for the high energy density and safety all-solid-state batteries.