Extremely stable Li-metal battery enabled by piezoelectric polyacrylonitrile quasi-solid-state electrolytes

Polymer solid-state electrolytes (PSSEs) are promising for solving the safety problem of Lithium (Li) metal batteries (LMBs). However, PSSEs with low modulus in nature are prone to be penetrated by lithium dendrites, resulting in short circuit of LMBs. Here, we design and prepare piezoelectric BaTiO3 doped polyacrylonitrile (PAN@BTO) quasi-solid-state electrolytes (PQSSEs) by electrostatic spinning method to suppress dendritic growth. The piezoelectric polymer electrolytes are squeezed by nucleation and growth processes of Li dendrites, which can generate a piezoelectric electric field to regulate the deposition of Li+ ions and eliminate lithium bud. Consequently, piezoelectric PAN@BTO PQSSEs enables highly stable Li plating/stripping cycling for over 2 000 h at 0.15 mA/cm2 at room temperature (RT, 25 °C). Also, LiFePO4|PAN@BTO|Li full cells demonstrate excellent cycle performance (136.9 mA·h/g and 78% retention after 600 cycles at 0.5 C) at RT. Moreover, LiFePO4|PAN@BTO|Li battery show extremely high safety and can still work normally under high-speed impact (2 Hz, ∼30 kPa). We construct an in-situ cell monitoring system and disclose that the mechanism of suppressed lithium dendrite is originated from the generation of opposite piezoelectric potential and the feedback speed of intermittent piezoelectric potential signals is extremely fast.